The invention relates to helmet mounted visual display systems, and more particularly, to an alignment tool and method for fitting a helmet to a user for accurate alignment with the helmet mounted visual display systems.
Various forms of military helmets are known according to the prior art. These helmets are constructed to protect the wearer""s head against injury while providing communication and life support. In addition modern combat requires military personnel to utilize certain helmet-mounted electronic systems, for example night vision systems and helmet mounted displays.
A problem arises when military personnel need to train with different electronic systems, for example, outer helmet mounted displays for several types of aircraft. These displays have exacting requirements for positioning relative to the wearer""s eyes. It has been determined that custom fitted inner helmets are necessary to meet such requirements. However, the outer helmets are too costly to custom fit every crewmember which will maintain or fly the aircraft.
Ideally, a custom fit inner helmet is provided to each individual. For example, an Inner Helmet Assembly pursuant to U.S. Pat. No. 5,584,073.
In order to properly position the inner helmet during custom fitting, a positioning fixture, as disclosed herein, may be utilized. The positioning fixture utilizes the latch assembly of the invention to attach to the inner helmet in the same manner as the ultimate outer helmet. The positioning fixture custom aligns the latch points on the inner helmet for each individual. The custom fittings are then secured to maintain the alignment in a reproducible manner. Accordingly, every custom fitted inner helmet provides a standard platform.
The outer helmets are then equipped with a uniform capture configuration to attach onto this standard platform via the latch assembly of the invention.
It is therefore a primary object of the present invention to provide a uniform capture assembly disposed on an outer device to latch onto a standard platform of an inner helmet.
It is another object of the present invention to provide a mounting surface on the outer device that assumes a predetermined orientation with respect to the inner helmet platform.
It is a further object of the invention to define a path for the outer device to follow during installation onto the inner helmet.
It is a further object of the invention to provide latch clearances that facilitate engagement and disengagement of the latch components.
It is another object of the invention to provide locking means for releasably securing an outer helmet onto the inner helmet.
These and other related objects are achieved according to an embodiment of the invention by providing a pair of strikers on flat temple panels of an inner helmet. An outer device or helmet includes a pair of inwardly-facing mounting surfaces that face the temple panels in the installed position. Ideally, the temple panels and mounting surfaces are all substantially parallel to each other. An arcuate channel assembly or track is disposed on each mounting surface for capturing a striker. The arc of the channel assembly corresponds to the curve generated by pivoting the outer device from front-to-back over a crown portion of the inner helmet into an installed position. For locking, quarter-turn fasteners located on the outer helmet may extend through holes in the lower, rear portion of the inner helmet to engage an interiorly-secured retention bar.
The channel assembly includes a base portion disposed adjacent the mounting surface, a central spacer portion and an upper portion. The tip end of the striker slidingly contacts the base portion during mounting of the outer helmet. The central spacer portion comprises a pair of arms spaced from the striker head by a distance D. The upper portion comprises a pair of rails spaced from the striker neck by a distance d that is less than D. The rails guide the neck portion along the length of the channel assembly and keep the head out of contact with the central spacer portion. The head and neck portions of the striker have a generally T-shaped cross-sectional profile. A concavity on the head or neck portion slidingly contacts facing regions of the upper portion.
The interchangeable latch system according to the invention is fitted for an outer helmet mounted display as follows. The inner helmet is placed onto the user and the internal fittings, straps, pads and/or cushions are adjusted to an approximate fit. The fitting fixture is installed onto the strikers. The fitting fixture includes fixed alignment guides that are used to view the user""s eyes along an eye line EL that is tangent to both of the front eyeball surfaces. Once aligned the connection line CL of the strikers is parallel to and separated from the eye line EL by a known and preset first vector V1 that is the same for all users.
An outer helmet display has a desired viewing distance VD from the users eyes. The outer helmet possesses a latch line LL that will be coincident with the inner helmet connection line CL. The distance between the outer helmet latch line LL and the display is defined by a second vector V2. The viewing distance VD is equal to V2 minus V1. Once V1 is established, the second vector V2 can be adjusted to obtain any desired viewing distance VD.
The inner helmet connection line CL is located in the quadrant above and rearwardly of the viewer""s eyeballs. In the vertical direction, CL is generally between the viewer""s eyes and the top of the head. The connection points comprise left and right connection points which are disposed in corresponding left and right vertical planes which are outwardly spaced from the viewer""s head. The latch points comprise left and right latch points which pivot within corresponding left and right vertical planes which are outwardly spaced from the viewer""s head. The viewing distance VD may extend along a horizontal line of sight wherein EL is perpendicular to VD. Where the first and second vectors V1 and V2 are in a common plane with the line of sight, V1 and V2 are perpendicular to EL.